Struct generational_indextree::Arena

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pub struct Arena<T> { /* private fields */ }

Expand description

An Arena structure containing certain Nodes.

Implementations

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impl<T> Arena<T>

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pub fn new() -> Arena<T>

Creates a new empty Arena.

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pub fn with_capacity(n: usize) -> Arena<T>

Create a new empty Arena with pre-allocated memory for n items.

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pub fn new_node(&mut self, data: T) -> NodeId

Creates a new node from its associated data.

Panics

Panics if the arena already has usize::max_value() nodes.

Examples

let mut arena = Arena::new();
let foo = arena.new_node("foo");

assert_eq!(*arena[foo].get(), "foo");

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pub fn new_node_with(&mut self, create: impl FnOnce(NodeId) -> T) -> NodeId

Creates a new node via specified create function.

create is called with the new node’s node ID, allowing nodes that know their own ID.

Panics

Panics if the arena already has usize::max_value() nodes.

Examples

let mut arena = Arena::new();
struct A { id: NodeId, val: u32 }
let foo = arena.new_node_with(|id| A { id, val: 10 });

assert_eq!(arena[foo].get().val, 10);
assert_eq!(arena[foo].get().id, foo);

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pub fn count(&self) -> usize

Counts the number of nodes in arena and returns it.

Examples

let mut arena = Arena::new();
let foo = arena.new_node("foo");
let _bar = arena.new_node("bar");
assert_eq!(arena.count(), 2);

foo.remove(&mut arena);
assert_eq!(arena.count(), 1);

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pub fn is_empty(&self) -> bool

Returns true if arena has no nodes, false otherwise.

Examples

let mut arena = Arena::new();
assert!(arena.is_empty());

let foo = arena.new_node("foo");
assert!(!arena.is_empty());

foo.remove(&mut arena);
assert!(arena.is_empty());

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pub fn get(&self, id: NodeId) -> Option<&Node<T>>

Returns a reference to the node with the given id if in the arena.

Returns None if not available.

Examples

let mut arena = Arena::new();
let foo = arena.new_node("foo");
assert_eq!(arena.get(foo).map(|node| *node.get()), Some("foo"));

Note that this does not check whether the given node ID is created by the arena.

let mut arena = Arena::new();
let foo = arena.new_node("foo");
let bar = arena.new_node("bar");
assert_eq!(arena.get(foo).map(|node| *node.get()), Some("foo"));

let mut another_arena = Arena::new();
let _ = another_arena.new_node("Another arena");
assert_eq!(another_arena.get(foo).map(|node| *node.get()), Some("Another arena"));
assert!(another_arena.get(bar).is_none());

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pub fn get_mut(&mut self, id: NodeId) -> Option<&mut Node<T>>

Returns a mutable reference to the node with the given id if in the arena.

Returns None if not available.

Examples

let mut arena = Arena::new();
let foo = arena.new_node("foo");
assert_eq!(arena.get(foo).map(|node| *node.get()), Some("foo"));

*arena.get_mut(foo).expect("The `foo` node exists").get_mut() = "FOO!";
assert_eq!(arena.get(foo).map(|node| *node.get()), Some("FOO!"));

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pub fn get2_mut(
 &mut self,
 i1: NodeId,
 i2: NodeId
) -> (Option<&mut Node<T>>, Option<&mut Node<T>>)

Get a pair of exclusive references to the elements at index i1 and i2 if it is in the arena.

If the element at index i1 or i2 is not in the arena, then None is returned for this element.

Panics

Panics if i1 and i2 are pointing to the same item of the arena.

Examples

use generational_indextree::Arena;

let mut arena = Arena::new();
let idx1 = arena.new_node("foo");
let idx2 = arena.new_node("bar");

{
    let (item1, item2) = arena.get2_mut(idx1, idx2);

    *item1.unwrap().get_mut() = "jig";
    *item2.unwrap().get_mut() = "saw";
}

assert_eq!(arena[idx1].get(), &"jig");
assert_eq!(arena[idx2].get(), &"saw");

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pub fn iter(&self) -> impl Iterator<Item = &Node<T>>

Returns an iterator of all nodes in the arena in storage-order.

Examples

let mut arena = Arena::new();
let _foo = arena.new_node("foo");
let _bar = arena.new_node("bar");

let mut iter = arena.iter();
assert_eq!(iter.next().map(|node| *node.get()), Some("foo"));
assert_eq!(iter.next().map(|node| *node.get()), Some("bar"));
assert_eq!(iter.next().map(|node| *node.get()), None);

let mut arena = Arena::new();
let _foo = arena.new_node("foo");
let bar = arena.new_node("bar");
bar.remove(&mut arena);

let mut iter = arena.iter();
assert_eq!(iter.next().map(|node| *node.get()), Some("foo"));
assert_eq!(iter.next().map(|node| *node.get()), None);

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pub fn iter_pairs(&self) -> impl Iterator<Item = (NodeId, &Node<T>)>

Returns an iterator of all pairs (NodeId, &Node) in the arena in storage-order.

let mut arena = Arena::new();
let _foo = arena.new_node("foo");
let _bar = arena.new_node("bar");

let mut iter = arena.iter_pairs();
assert_eq!(iter.next().map(|node| (node.0, *node.1.get())), Some((_foo, "foo")));
assert_eq!(iter.next().map(|node| (node.0, *node.1.get())), Some((_bar, "bar")));
assert_eq!(iter.next().map(|node| (node.0, *node.1.get())), None);